Respirators

ABSTRACT

A respirator ( 1 ) having a plurality of internal masks ( 2, 3 ) within an external mask ( 4 ), the inner masks ( 2, 3 ) being linked by ducts ( 8, 9 ) so as to direct the inhaled air from the outside of the mask to the oronasal area via an ocular mask. The oronasal mask ( 3 ) has a secondary valve ( 12 ) that is sprung so as to operate within the timeframe of the exhalation part of the breathing cycle, the exhaled air being ejected into the hollow outer body of the mask ( 4 ).

Cross Reference to Related Applications

This application is the U.S. national phase of International ApplicationNo. PCT/GB03/00689 filed on Feb. 13, 2003 and published in English asInternational Publication No. WO 03/0683 18 Al on Aug. 21, 2003, whichapplication claims priority to Great Britain Application No. 0203701.8filed on Feb. 16, 2002, the contents of which are incorporated byreference herein.

This invention relates to respirators and provides a respirator withdistinct inner masks, in order to give the wearer extra protection,which are designed to use the inhaled and exhaled air to enhance theeffectiveness of the respirator.

Respirators which enable workers to operate in hazardous environmentshaving airborne contaminants, commonly rely on the exhaled air of thewearer to produce a positive pressure inside the mask. Thus if there isany leakage into the mask where it forms a seal with the wearer's head,or if the mask's containment is breached, the exhaled air will flow outfrom the mask, purging the mask and transporting any contaminatedambient air away.

However, the pressure inside conventional respirators falls belowambient on inhalation, so that inward leakage may occur, enablingcontaminants to enter the inside of the mask. Any contaminants insidethe mask can cause harm or discomfort to the wearer, particularly ifthey are free to attack the eyes or oronasal cavities.

Masks have been designed to overcome the problem of in—leakage, usuallyby incorporating mechanical pumps and such like to maintain a positivepressure inside the respirator. Such devices are not fail-safe however,and add weight to the mask. Where the exhaled air is conventionally usedto increase the pressure inside the mask, it requires breathing effortto maintain the higher interior pressure which is uncomfortable andtiring for the wearer.

A second known problem of respirators that incorporate an eyepiece isthat the eyepiece is often prone to misting. This can be partiallyovercome by causing the inhaled air to flow over the eyepiece anddirecting the exhaled air away from the eyepiece. However, in suchrespirators there is a disadvantage in that any contaminated air thatleaks into the mask will be caused to flow over the eyepieces, attackingthe eyes.

It would be advantageous, therefore, to develop a respirator in whichboth the inhaled and exhaled air contribute to the functionality of themask without resorting to mechanical means to maintain a pressure levelabove ambient, whilst building in added protection for the vulnerableeyes and oronasal cavities.

Accordingly, the present invention provides for a respirator comprisingat least one integral eyepiece, at least one inlet valve to admitinhaled air and at least one outlet valve to control the egress ofexhaled air, characterised in that the respirator further comprises aplurality of inner masks enclosed within an outer mask to form a maskcavity between the inner masks and outer mask when worn, at least oneinner mask being an oronasal mask, and at least one other inner maskbeing an ocular mask, and wherein at least some of the exhaled air isdirected into the mask cavity so as to achieve a super-ambient pressurein the mask cavity.

The advantage of this configuration is that by employing a close fittinginner oronasal mask the drop in pressure due to inhalation will belocalised in this mask, and any other masks linked to it by ducting, andtherefore, there will be no pressure drop in the mask cavity. Also theuse of inner masks for the eyes and oronasal areas provides the wearerwith two layers of protection from contamination.

By ensuring that some proportion of the exhaled air is directed into themask cavity, the pressure in that part can be maintained above ambient.The oronasal mask could conveniently be provided with a valve to allowsome or all of the exhaled air to be directed into the mask cavity ateach exhalation.

The operation of the respirator can be usefully facilitated by employinga main outlet duct or passage from the oronasal area to duct some of theexhaled air away from the mask, conveniently with a non-return valve,and a secondary valve in the oronasal mask to vent some air into themask cavity.

Advantageously, the main air outlet can be directed into a chamber ofthe mask to form a further seal, or vented to outside the mask asrequired.

The secondary valve might conveniently be on a weak spring, or any othersuitable return mechanism, that opens and closes at a slight,predetermined over pressure in the oronasal mask. This has the advantagethat during the exhale cycle the valve can be made to open and closewithin the timeframe of the egress of the exhaled air, so that the valvereleases any pressure in the oronasal mask into the mask cavity, andcloses readily, keeping the mask cavity at above ambient pressurethroughout the breathing cycle, even when the pressure in the oronasalmask drops below ambient.

The eyepiece may be held in a single ocular mask, or may be in the formof goggles, and may be linked to the oronasal mask. In such a case,there may be a non return valve or similar mechanism between theoronasal mask and the ocular mask, so that exhaled air is not directedback over the mask's eyepiece.

These inner masks would advantageously be made close fitting and may beequipped with seals to ensure that they are substantially air tight,providing a second level of protection for the more vulnerable areas ofthe face, and further ensuring that during inhalation, pressure dropsare contained within the internal masks.

In order to prevent misting, inhaled air can be drawn into the mask andpassed via ducts, over the eyepiece of the ocular mask before beingdirected towards the oronasal region. By ensuring that the inhaled airis ducted through an ocular mask, rather than simply being guided acrossthe eyepiece, more of the air flow can be employed for demisting.Additionally, the use of a non-return valve between the ocular mask andthe oronasal mask, reduces the possibility of wet exhaled air mixingwith this airflow to fog the mask.

Furthermore, in other masks in which the air is used to clear theeyepiece, the eyes are open to the outer region of the mask, so thatshould there be a breach of containment, the eyes could be attacked bychemicals. In this new configuration, the air is ducted to the oronasalarea, via the ocular mask or masks from outside. There is no mixing ofinhaled air and air from the mask cavity, so even if the mask cavity isbreached, the eyes are protected and the mask maintains an eyepiececlearing function.

The eyepiece of the ocular mask may be entirely separate from the outermask, there being an eyepiece in each, or the eyepiece of the ocularmask could form a single eyepiece, the outer mask being formed aroundthis part of the mask, so that there is a common eyepiece between theinner and outer masks.

The external mask of the respirator might be a flexible hood,conveniently made of a resilient material such as rubber. Around theperiphery of the external mask there would advantageously be provided aseal between the mask and the head.

The mask cavity would be formed between this seal and the seal aroundthe oronasal and ocular masks, to create a volume capable of being keptat super ambient pressure during use.

An embodiment of the invention will now be described by way of exampleonly with reference to the accompanying drawing, wherein

FIG. 1 is a front vertical section, of the respirator.

With reference to FIG. 1, a respirator 1 comprises two separate innermasks 2, 3 within the body of the respirator 1 so as to form a maskcavity 4 inside the outer mask. Both the ocular mask 2 and the oronasalmask 3 have seals 5,6 respectively to ensure a close, substantiallyairtight fit with the wearer. Inhaled air is drawn via ducts 8, 9 fromthe outside 7, and over the eyepiece of the ocular mask 2, before beingdrawn into the oronasal mask 3. Exhaled air is exhaled via a valve 10 tothe outside 7. The eyepiece of the ocular mask forms the eyepiece of therespirator, the outer mask being sealed around the periphery of theocular mask.

The inlet duct 9 to the oronasal mask is supplied with a non returnvalve 11 and a secondary valve 12, which is sprung so that it opensafter the main valve 10 opens, and closes before the main valve closes.i.e. it operates within the time frame of the exhalation part of thebreathing cycle. This secondary valve 12 allows exhaled air to be ventedinto the mask cavity 4 of the outer mask. The use of such a releasevalve that opens easily at a slight excess pressure allows the wearer toexhale freely into the cavity, but prevents a decrease in pressure inthe mask cavity on inhalation. The outer mask forms a seal 13 with thewearer's head, ensuring that the pressure inside the mask remainssuper-ambient.

1. A respirator comprising at least one inlet valve to admit inhaled air and at least one first outlet valve to control the egress of exhaled air, the respirator further comprising a plurality of inner masks enclosed within an outer mask to form a mask cavity between the inner masks and outer mask when worn, at least one inner mask being an oronasal mask, and at least one other inner mask being an ocular mask, wherein the oronasel mask is in fluid communication with the first outlet valve and a second outlet valve, the first outlet valve adapted to direct at least some of the exhaled air outside the respirator and the second outlet valve adapted to direct at least some of the exhaled air into the mask cavity so as to achieve a super-ambient pressure in the mask cavity.
 2. A respirator as claimed in claim 1, wherein the inner masks are connected to the ambient atmosphere by ducts.
 3. A respirator as claimed in claim 2 wherein the masks are linked so as to form an inhalation air path from ambient via the ocular mask or masks to the oronasal area.
 4. A respirator as claimed in claim 3 in which the air path between the oronasal and ocular masks is provided with a non-return valve.
 5. A respirator as claimed in any of the preceding claims in which the outer mask of the respirator, and the inner ocular mask or masks share a common eyepiece.
 6. A respirator as claimed in claim 1, further comprising an eyepiece in the ocular mask or masks that is distinct from an eyepiece in the outer mask of the respirator.
 7. A respirator as claimed in claim 1, wherein the first outlet valve is adapted to allow exhaled air to pass during the whole of the exhalation part of the breathing cycle, and the second outlet valve is capable of venting exhaled air into the mask cavity, opening and closing within the timeframe of the exhalation part of the breathing cycle. 